Revetment mat



Patented Aug. 18, 1936 UNITED STATES REVETMENT MAT William L. Schloss and Edgar G.. Bell, Cleveland, Ohio N Drawing. Application January 16, 1935, Serial No. 2,124

1 Claim. (CI. 61-38) The invention relates to the protection of river banks and the like against erosion, washing and frost.

It is well known that the banks of bodies of 5 water, particularly rivers, Wash away not only as x the result of flood conditions but also in the natural course of erosion produced by the flowing water and in innumerable instances this has caused incalculable property damage and loss of life. It has been proposed to protect the banks by means of various expedients such for instance as slabs of concrete flexibly connected by some means or other or else by mats of bituminous material likewise usually connected by some metallic means or other and supposed to rest upon the river bank and a portion of the bottom adjacent the bank and extending preferably an appreciable distance outwardly therefrom. However, without being especially derogatory in regard to the efiorts of engineers and others in curing the dangerous condition, it has been found that there are numerous disadvantages in and objections to known methods of protection. Notably metallic connections between concrete slabs or asphalt mats corrode in a short time on account of the presence of acids or other chemicals in the water, a condition which is particularlyprevalent in cases where a river is used to carry oif wastes from industrial plants of different v types. In addition, concrete slabs leave exposedan excessive proportion of the area of'the river bank and bottom and on account of the inherent characteristics of concrete are unable to conform sufficiently closely to the contour of thebank or bottom to avoid danger of erosion of the surface beneath the slabs. As regards asphalt mats of known construction, the same objection is prescut as to corrosion of any metallic connecting means if such be used. The character of as-- to phalt mats is such that they may be expected to' retain or possess a certain amount of plasticity so as to conform rather more closely to the contour of the river bank and bottom than is the case with concrete slabs, but unless asphalt mats be constructed of very heavy embedded metallic reinforcements or else be made of such thickness as to impair the highly desirable and in fact necessary plasticity to conform to the surface of the underlying river bank or river bed such mats sink 5i) but slowly and might therefore be in danger of displacement in the event of extraordinarily high water and unusually rapid currents;

It is with all of the above facts and conditions in view that the present invention has been designed, the principal object of which is to provide asphalt mats of such construction as to avoid the use of metallic connections between them and to enable them to be suiiiciently heavy to sink rapidly and be stable and at the same time sufiiciently thin that they will accommodate themselves even 5 to comparatively sharply irregular contours of the river bank and bottom and moreover to reestablish such conforming engagement even though the underlying surface maybe eroded or scoured away by unusual currents. 10 It is another object ofthe invention to provide revetment mats of this character which may or may not embody embedded metallic reinforcing means such as expanded metal of different varieties, chains, wire networks or any of such means 15 known in the art. 7

A further object of the invention is to pro-- vide a revetment mat which need not be made at some remote point and shipped to the place of use but which may conveniently be produced 2 on a'scow or the like and fed overboard where needed, different detailed modes of production being possible.

A' more'specific object of the invention is to' provide a revetment mat consisting principally of 2:, some appropriate bituminous material, for instance asphalt which is mixed with an inert fillersuch as hydrated lime, carbonate of lime, lime dust, silicate dust or the like and an admixture of an appropriate proportion of a weighting ma- 30,-

terial preferably pulverized iron oxide of the variety found in nature in profuse quantities at many localities and which is therefore available at slight cost, these various ingredients constituting a homogeneous and tenacious whole whichasl may be formed into unusually thin sheets so as to obtain maximum plasticity under even unusual conditions of service'without sacrificing toughness, tensile strength and necessary weight, all

of these advantageous resultsibeing obtainable to,

such as hydratedlime, carbonate of lime, lime. 5s

dust silicate dust or the like together withv a weight increasing substance preferably iron oxide in the form of iron are such as is found in nature. While it is probable that the proportions of different ingredients may be variedv within at 5.5-

least certain limits, it has been found that a very satisfactory product is obtained by using, for example, a material composed by volume of 50 parts of asphalt, 42 parts of the hydrated lime or its equivalent and 8 parts of the iron oxide. Another highly satisfactory composition has been found to be: asphalt 57.5%, limestone dust 33.6% and iron ore 8.9%, all by volume. acteristics of the pulverulent calciferous materials are such that they readily mix with the asphalt or other bituminous material for forming a homogeneous sheet and it is clear that these sheets may be cast in shallow molds or, conceivably, rolled out.

While it is not essential it is certainly convenient that this work be carried out on board a scow which may be moored or moved slowly along at the particular location where revetment mats are needed. Clearly, especially if the rolling method of production is restored to the sheets or mats may be made of indeterminate size and in case the casting or molding operation is resorted to it'is apparent that the mats may likewise be of widely varying sizes depending upon,

or contingent upon manufacturing limitations in so far as regards sizes of molds and difliculties in handling the material prior to and after molding. It is well within the purview of the invention, particularly when casting the mats, to provide a reinforcement which may consist, for instance, of a wire network, expanded sheet metal or anything else of a similar nature which will extend throughout the mat and thereby greatly increase its tensile strength, it being naturally a restriction that such reinforcing should not be so heavy or rigid as to impair the flexibility of the mat and interfere with its ability to conform to the uneven surfaces which usually constitute the contour of river banks and the bottom adjacent the bank.

Regardless of whether the mats be produced at some more or less remote point and transported where their use is necessary or whether the mats be formed substantially immediately adjacent their place of use, the idea is that they should be fed overboard, with possibly appropriate guide means and more or less skillful handling so that they will settle into the water and consequently lie upon the surface of the ground where protection is needed. It is clear that such mats should be shingled or in other words laid in overlapping relation with the overlapping portions extending down stream in order to prevent water currents from entering the overlappingjoints to any material extent and eroding away the underlying earth surface.

In actual practice it has been found that mats properly constructed in the manner above set forth, or in some equivalent way, have the faculty, on account of the additional weight afforded by the presence of the iron oxide, of settling quickly through the water and coming to rest on the bottom without likelihood of lateral displacement on the way and as a consequence the shingling above referred to may be readily accomplished so that there will be no exposed earth surfaces between successive or adjacent mats. Moreover the additional weight afforded by the presence of the iron oxide combined with the relative thinness of the mats, which may actually be made as little as a half inch or so thick, in conjunction with the natural plasticity of the material will cause the mats to conform closely to whatever inequalities there may be in the surfaces to be protected. In addition, it is The charwater and will therefore not be subject to corrosion by acids or other chemicals which may be present in the water. In addition, as there are no metallic elements connecting the mats in chains 15 or in series there is nothing in the way of metal exposed which might be eaten away and render the mats liable to separation or other displacement.

Under some circumstances, that is to say in tropical countries or wherever the temperature is constantly comparatively high, it is possible to reduce the asphalt content to a material extent and possibly to thicken the mat in view of the fact that the high temperature will prevent the asphalt from becoming brittle. Another pcintto be considered is that in cases where the mats are laid in such manner that they will extend up onto and cover the bank beyond the water line the mats will protect the banks against erosion or Washing away as the result of rain storms. Moreover, in all instances, the presence of the mats will prevent damage, or at least reduce danger of damage, to the banks as the result of frost.

From the foregoing description it will be ap-- parent that there has thus been provided a very simply constructed and highly inexpensive revetment mat which may be readily produced and installed or employed in a rapid manner and which will efficiently perform all the functions of protecting river banks and the like against the destructive action of water currents, rain and frost, and which will moreover possess the advantages sought after and set forth in the forepart of this specification.

In connection with the use of the word asphalt throughout the specification, it should be understood that this material may be Trinidad or other natural asphalt, artificial asphalt, a blend of natural and artificial asphalts, orbitumen which, as is well known, consists of asphalt tempered with asphaltic oil.

While there have been described certain specific ingredients and more or less definite proportions thereof, together with a rsum of conceivable 1 modes of production of the mats it should be understood that the disclosure is principally an exemplification of the essential feaures involved as the right is reserved to make all such changes in different aspects of the invention as will widen the field of utility and increase the adaptability, provided such variations constitute no departure from the spirit of the invention or the scope of the claim hereunto appended.

Having thus described the invention, what is claimed is:

A revetment mat for the protection of river banks comprising a flexible sheet of asphaltic, self-conforming material, consisting of approximately, by volume, 50-57 parts of asphalt, 42-33% parts of pulverized calciferous material, and as remainder pulverized iron oxide.

WILLIAM L. SCHLOSS.

EDGAR G. BELL. 

